1. Field of the Invention
This invention relates to an information signal recording apparatus and more particularly to an apparatus arranged to record pilot signals along with the information signal for tracking control.
2. Description of the Related Art
In the field of the apparatuses of the kind using rotary heads for recording and/or reproducing signals by tracing a magnetic tape, research and development work has come to be actively conducted during recent years for digital tape recorders which record and reproduce digital data instead of analog signals. In recording and reproducing a video signal such as a standard television signal in real time with such a digital tape recorder, the amount of coded data becomes very large. The large amount necessitates high density magnetic recording. In addition, high speed data recording is necessary as the amount of data to be recorded or reproduced per unit time is also very large.
The so-called multi-track recording arrangement in which a plurality of recording tracks are simultaneously formed is considered to be a method for meeting these requirements. Further, to lessen the track pitch as much as possible in carrying out multi-track recording with a rotary head, there has been contrived a so-called azimuth overlap writing method in which adjacent recording tracks are arranged to have different magnetizing directions with no guard band provided between them.
Generally, it is important for a rotary head type magnetic recording and/or reproducing apparatus to perform tracking control over the head during a reproducing operation to have the head accurately trace the recording tracks. The tracking control methods employed by the conventional rotary head type magnetic recording and/or reproducing apparatus include a method in which control signals (hereinafter referred to as the CTL signal) for tracking control are longitudinally recorded along the edge of a magnetic tape and another method called the four frequency method in which pilot signals of four different kinds are superimposed on information signals.
However, the method of using the CTL signal is not suited for high density magnetic recording because it necessitates the provision of an additional track specially allocated for the control signal. Besides, tracking control cannot be accurately accomplished by this method because of a mismatch which tends to arise between the actual recording track and the CTL signal.
As regards the four frequency method and particularly in the event of multi-track recording, a plurality of different kinds among four different kinds of the pilot signals must be selectively generated. Besides, a signal processing operation for obtaining a tracking error signal becomes complex accordingly. Therefore, the four frequency method results in an excessively large hardware arrangement. Further, even if the tracking error signal obtaining hardware is thus arranged, a plurality of tracking error signals would simultaneously be generated. Then, the simultaneously generated tracking error signals must be adequately processed. The four frequency tracking control method is therefore not suitable for multi-track recording. Further, in the event of frequency multiplexing the pilot signals along with digital video signals, it affects the modulated waves of the digital video signals. Hence, this brings about an increased rate of error during recording or reproduction. It is conceivable to solve this problem by multiplexing the tracking control pilot signals in a time-sharing manner along with the digital video signals. However, this arrangement is also not desirable as it decreases a video signal recordable area.